Unstretched canvases allow you to frame or mount the canvas on your own or at a future date.
Unstretched canvases are carefully rolled and shipped inside a sturdy tube.
Allow 1-2 weeks for unstretched canvases to arrive

Stretched canvases are mounted and ready to hang but are not framed
Stretched canvases are shipped flat.
Allow 2-3 weeks for your stretched canvas to arrive.